Process for producing pulp



Patented Dec. 8, 1925.

UNITED STATES PATENT OFFICE.

WILLIAM D. GREGOR, WESLEY M. OSBORNE, AND ALEX J. KEMZURA, OF NEWTON FALLS, NEW YORK.

PROCESS FOR PRODUCING PULP.

No Drawing.

To all whom it may concern:

Be it known that we, WILLIAM D. Gnnoon, lVEsLnr M. OSBORNE, and ALEX J. KEMZURA, citizens of the United States, residing at Newton Falls, in the county of St. Lawrence, State of New York, and Newton Falls, in the county of St. Lawrence, State of New York, and Newton Falls, in the county of St. Lawrence, State of New York, respectively, have invented certain new and useful Improvements in Processes for Pro- 'ducing Pulp, of which the following is a specification.

The present invention relates to the production of pulp used in the manufacture of paper and like products from the various fibrous materials suitable for these purposes.

More particularly the invention relates to processes for cooking materials, such for example, as hard woods which have not been heretofore successfully used in the production of bleachable pulps used in the manufacture of high grade papers.

The objects of the invention are to provide an improved, more effective, and more efficient process of cooking materials to produce pulps; to provide a cooking process whereby high grade bleachable fibres may be produced from hard woods and like materials not heretofore successfully used, and which may be used in the production of high grade papers; and such other objects as may be attained by utilization of the various novel steps and principles hereinafter set forth.

The novel and highly useful results are in general attained by cooking in a manner to cause a circulation of the chips, steaming slowly for a long period, and then cooking rapidly. The peculiar reactions which produce the improved pulp are undetermined, and an understanding thereof is not necessary to carry out the invention. Although certain steps and values are set forth to give the most effective results, it is to be understood that the procedure and steps may vary within wide limits and certain of the steps may be eliminated without departing from the spirit of the invention.

In carrying out the invention, the following method has produced unusually good results with hard woods. The digester or cooker is partially filled with any usual cooking liquor, preferably so-called sulphite acid of usual strength. The wood which Application filed July 14, 1924. Serial No. 725,983.

has been reduced to chips in well known manner, is then fed into the partially filled digester in an amount sulficient to loosely fill the same up to the proper level after the remaining cooking liquor has been supplied. When the proper amount of chips has been supplied, the digester is filled finally to the proper level with cooking liquor, the cover is fastened in place, and the proper connections are made.

One of the main features of the invention is to establish a proper circulation of the contents which is accomplished as follows:

The gas valve is closed, and steam is slowly admitted for a period of about two minutes at the initial slow rate, and thereafter at two minute intervals the rate of ad mission of steam is slightly increased until a ar is noted due to circulation of the contents which will be brought about by this method of admitting the steam. After the jar or circulation of contents is reached, the steam is admitted in a manner to slowly bring the digester pressure to approximately seventy pounds per square inch. Effective results are attained when the time consumed from the first admission of steam is about two and one-half hours. When the pressure of seventy pounds has been reached, the presure is slowly relieved and the admission of steam is so regulated as to maintain the pressure at seventy pounds for a relatively long period. Having established a proper circulation in bringing the pressure up to seventy pounds, the chips remain in circulation during the period of slow steaming. In the treatment of hard woods, this slow steaming should be carried out for about five and one-half hours -although this time may vary very widely in accordance with materials treated and the strength of the cooking liquor.

At the end of the slow steaming period, during which the proper temperatures are maintained by the pressure control set forth, steam is admitted rapidly and the pressure is rapidly relieved in a manner to produce rapid cooking, while maintaining the digester pressure of seventy pounds. The final rapid cooking is carried on until the cooking liquor reaches a predetermined strength, and the cooking is then complete.

In the sulphite process, the final rapid cooking is carried on until the total SO in the liquor reaches an approximate value of 0.05 percent. The point at which the proper strength of liquor is reached which marks the completion of the process may be determined in any convenient manner, as by sampling from a test cock towards the completion of the cooking and blowing on the Iodine test to determine the S0 content of sulphite cooking liquor. Although ,a value of 0.05 percent SO has given effective results in practice, it will, of course, be understood that this Value may be varied for dilfering grades of pulps and the best Value may be readily determined by trial for each individual case.

When the predetermined strength of liquor is shown, the contents of the digester are blown at seventy pounds pressure into the blow pit, washed and screened in the usual manner, and are then ready to be used unbleached, or to be sent to the bleachery.

Sulphite pulp produced from hard woods by the improved process as described is very close in appearance and properties to Esparto pulp, but is bleachable to a bright white color. High grade white papers may be made therefrom, which is evenly closed up and free fromfuzz or line fibers which rise up on the sheet.

Having described a preferred embodiment of the invention, what is desired to be secured by Letters Patent and claimed as new is:

1. The process of digesting materials to form pulp which comprises the steps of partially filling the digester with cooking liquor,.feeding the material into the partially filled digester an amount which will permit circulation of material in the liquor during the cooking, then filling in the remaining amount of cooking liquor to complete the charge.

2. The process of digesting material to form pulp which comprises the step of charging the digester with cooking liquor and filling loosely with chips of the material in a manner to permit circulation of the material during cooking of the charge.

3. The process of digesting materials to form pulp which comprises charging the digester with cooking liquor and material in a manner to permit circulation of the contents and admitting steam in a manner to cause circulation of the contents and at the same time gradually increasing the temperaturethereof.

4. The process of digesting materials to form pulp which comprises charging the digester with cooking liquor and material; admitting steam slowly until a predetermined pressure is attained in the cooker in a manner which will cause circulation of the material in the liquor during cooking; then slowly admitting steam and relieving the pressure in the digestor to maintain said predetermined pressure therein for a pre detern'iined time interval; and then admitting steam and relieving the pressure rapidly in a manner to cause rapid cooking of the contents at said predetermined pressure after said SlOW steaming is completed.

5. The process as set forth in claim 4 in which the rapid cooking is carried on until a predetermined strength of cooking liquor is attained.

6. The process of cooking materials to form pulp which comprises charging a digester with cooking liquor and material, subjecting the charge to slow steaming under predetermined pressure for a predetermined time in a manner to maintain a circulation of materials in the cooking liquor, then rapidly steaming the contents until a predetermined strength of cooking liquor is obtained which marks the completion of the process.

7. The process of cooking materials which comprises the steps of charging a digester with cooking liquor and material, slowly'cooking the contents for a predetermined time interval at a predetermined pressure in a manner to maintain a circulation of materials in the cooking liquor, and then cooking the same rapidly until a predetermined strength of cooking liquor is attained at which the cooking is complete.

Tn testimony whereof, we atl'ix our natures.

W. I). GREGOR. W. M. OSBORNE. ALEX J. KEMZURA. 

